The invention relates to multiple element electroacoustic transducing.
For background reference is made to U.S. Pat. No. 4,008,374.
It is an important object of the invention to provide an improved multiple element electroacoustic transducer.
According to the invention, there is an enclosure supporting a first loudspeaker driver assembly and a second loudspeaker driver assembly and having an internal volume. At least the first loudspeaker driver assembly is constructed and arranged to radiate sound energy into the listening region outside the enclosure over a first range of audio frequencies above a predetermined first frequency and a predetermined second frequency higher than the first frequency. The second loudspeaker driver assembly is constructed and arranged to radiate sound energy over a first predetermined range of audio frequencies embracing at least the range of audio frequencies between the first frequency and the second frequency. The first loudspeaker driver assembly, the second loudspeaker driver assembly and the enclosure are constructed and arranged to coact to maintain the pressure in the enclosure substantially constant over at least the range of frequencies between the first and second frequencies. The first predetermined range of audio frequencies may be substantially the full audio frequency range, or may correspond substantially to the bass frequency range. There may be an audio signal input and a low-pass filter coupling the audio signal input to the second loudspeaker driver assembly, and a high-pass filter coupling the audio signal input to the first loudspeaker driver assembly. The first loudspeaker driver assembly may comprise a number of loudspeaker drivers. There may be an audio signal input including a plurality of input channels coupled to respective ones of the loudspeaker drivers, and a summer coupling the input channels to the second loudspeaker driver assembly. The enclosure may include first and second ports coupling the first and second loudspeaker driver assembly to the listening region outside the enclosure.
The second loudspeaker driver assembly may be constructed and arranged to radiate to the listening region outside the enclosure through an acoustic impedance, such as an acoustic waveguide or port, or be coupled to an enclosed chamber.
In a specific form of the invention, the acoustic impedance may be an acoustic waveguide having one end closed and the other end open. In a specific form, the second loudspeaker driver assembly may be mounted such that the distance from the loudspeaker assembly to the open end is about twice the distance to the closed end. In another specific form, the acoustic impedance may be a ported or unported chamber.
According to a specific form of the invention the first loudspeaker assembly may have more loudspeaker drivers than the second loudspeaker assembly, and both assemblies may be limited to operating over the same bass frequency range.